PARIS — European Space Agency (ESA) managers, with an endorsement from an independent inquiry board, have agreed to solicit bids beginning March 5 for two new space-science missions and extend the operations of successful satellites now orbiting Mars and Venus.

The solicitation will seek proposals for two missions with a combined budget of 950 million euros ($1.25 billion) and launch dates between 2016 and 2018.

ESA’s Science Program Committee (SPC) agreed to make the move despite the fact that Europe’s space-science budget is already fully committed. But a guarantee from ESA Science Director David Southwood that he could find 200 million euros in savings from the existing program convinced the SPC to authorize the new spending.

In a Feb. 28 interview, Southwood said he and the SPC have agreed on the steps needed to find the savings, which in part come from cutting ESA science personnel costs by not replacing retiring employees in the coming years.

“We’re going to do this as painlessly as we can,” Southwood said. “I would prefer not to do it at all, but we need to prepare the future and right now we are eating our seed corn. We cannot continue in this way.”

Other savings will be made by shutting down operating satellites whose scientific value has been largely exhausted, and by making ESA’s Solar Orbiter mission part of NASA’s Living with a Planet Sentinels program. This last change will save 120 million euros — pending an agreement with NASA that ESA hopes to conclude late this year.

But ESA’s current science program places as many new expenses in Southwood’s in-box as are removed through savings.

The latest example is the Feb. 22 agreement by the SPC to extend, to May 2009, the operations of the successful Mars Express and Venus Express satellites. The combined cost is about 11 million euros.

ESA and the SPC say the agency’s science missions have an excellent track record of remaining on budget compared to any other space program, but cost increases do occur. The most recent examples:

   ESA’s contribution to the NASA-led James Webb Space Telescope, originally budgeted at 160 million euros for the ESA-provided instruments, is now expected to cost 173.6 million euros. This figure does not include 23.6 million euros in operating costs to be incurred by ESA. Also not included is the ESA-supplied launch aboard a European Ariane 5 heavy-lift rocket, whose cost to ESA will be about 150 million euros.

   The Lisa Pathfinder mission, designed to prove technologies for the future ESA-NASA Lisa satellite, continues to encounter technical challenges. Its budget of 185 million euros in early 2006 has now climbed to 226.5 million euros, and its launch has been postponed beyond 2009 to a yet-undetermined date.

   The BepiColombo mission to Mercury in 2013, which includes a Japanese-provided satellite, is expected to cost 665 million euros, 15 million euros more than the cost projections of a year ago.

ESA officials, including Southwood, had warned European space scientists and the SPC in 2006 that the program was overbooked and risked the space-science equivalent of Chapter 11 bankruptcy if one of its large missions ran into budget trouble.

ESA’s science budget is set at about 400 million euros per year. The agency’s member governments in December 2005 agreed to a 2.5 percent annual increase in science spending for five years.

The risks of an overextended science program led to the appointment in late 2006 of an outside panel to review the way Europe selects, finances and manages space-science projects.

The nine-member panel, called the Science Program Review Team, was chaired by Reinder van Duinen of Holland, current president of the European Science Foundation and a former executive with Fokker Aircraft B.V. and Fokker’s space division.

Van Duinen’s report was submitted to the SPC Feb. 22 and will be reviewed by ESA’s ruling council March 14 before being made public.

But Southwood said the panel’s investigation — “I treated this review as a kind of audit,” he said — has already helped shape the decision to insist on 200 million euros in savings in part by cutting operations for long-serving satellites.

In a March 1 interview, van Duinen said the panel urged ESA to readjust its spending so that less is spent maintaining existing satellites and more spent on designing new missions.

“If we did not agree to solicit new missions now, we would have had to wait until 2020 or later,” van Duinen said, adding that the panel urged ESA to find “at least” 200 million euros in savings to provide budgetary clearance for the new missions.